Flexible circuit board with improved bonding position accuracy

ABSTRACT

In one example, a flexible circuit board includes a signal line disposed between a first ground and a second ground; a dielectric disposed between the first ground and the signal line and between the second ground and the signal line; a cover layer disposed below the first ground and having openings formed therein such that the first ground is exposed at certain intervals; and a position alignment portion formed across the opening and configured to bisect an area of the opening.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional Application of U.S. Ser. No.16/224,975, filed on Dec. 19, 2018, which claims the benefit under 35U.S.C. § 119 of a Korean patent application No. 10-2018-0009432 filed onJan. 25, 2018 in the Korean Intellectual Property Office, the entiredisclosures of which are hereby incorporated herein by reference.

TECHNICAL FIELD

The embodiments described herein pertain generally to a flexible circuitboard.

BACKGROUND

Recently, a flexible circuit board has gradually replaced a coaxialcable, which has been used for the purpose of transmitting a highfrequency signal as a component of wireless terminals such as asmartphone and a tablet personal computer (PC).

In addition, surface mounter technology (SMT) has been used as a methodof bonding the flexible circuit board to a printed circuit board.

As shown in FIG. 1, according to the SMT, a flexible circuit board 10 ismounted on a printed circuit board 20, and the flexible circuit board 10and the printed circuit board 20 are coupled by thermally melting solder22 between a flexible circuit board ground pad 11 formed below theflexible circuit board 10 and a printed circuit board ground pad 21formed on the printed circuit board 20.

However, when the flexible circuit board 10 is not properly mounted onthe printed circuit board 20, the SMT is not properly performed.

SUMMARY

The present invention has been made to solve the above-mentionedconventional problems and is directed to providing a flexible circuitboard with improved bonding position accuracy.

In one example embodiment, a flexible circuit board with improvedbonding position accuracy includes: a signal line disposed between afirst ground and a second ground; a dielectric disposed between thefirst ground and the signal line and between the second ground and thesignal line; a cover layer disposed below the first ground and havingopenings formed therein such that the first ground is exposed at certainintervals; and a position alignment portion formed across the openingand configured to bisect an area of the opening.

The position alignment portion may be formed in a diagonal shape.

An area of an upper left side of the opening bisected by the positionalignment portion may be equal to an area of a lower right side of theopening bisected by the position alignment portion, and an area of anupper right side of the opening bisected by the position alignmentportion may be equal to an area of a lower left side of the openingbisected by the position alignment portion.

The diagonal shape of the position alignment portion formed in theopening may be symmetrical to a diagonal shape of a position alignmentportion formed in another opening adjacent to the opening.

In another example embodiment, a flexible circuit board with improvedbonding position accuracy includes: a signal line disposed between afirst ground and a second ground; a dielectric disposed between thefirst ground and the signal line and between the second ground and thesignal line; via holes formed in a direction orthogonal to a lengthwisedirection of the signal line, passing through the first ground, thesecond ground, and the dielectric in a vertical direction, and formed byfilling a plurality of holes, which are formed in the vertical directionsuch that the first ground and the second ground are electricallyconnected, with conductors; and a cover layer disposed below the firstground and having openings formed therein such that the via holes areexposed at certain intervals.

The flexible circuit board may further include printed circuit boardground pads coupled to the openings via solder, wherein the printedcircuit board ground pads may be formed to be long in a widthwisedirection of the signal line at both sides of the signal line interposedtherebetween, an inner side of each of the printed circuit board groundpads in the widthwise direction may be formed in a shape the same as ashape obtained by bisecting the opening along a center thereof, and anouter side of each of the printed circuit board ground pads in thewidthwise direction may be formed in a shape which extends to have asize equal to a diameter of the opening.

In yet another example embodiment, a flexible circuit board withimproved bonding position accuracy includes: a signal line disposedbetween a first ground and a second ground; a dielectric disposedbetween the first ground and the signal line and between the secondground and the signal line; ground connection portions formed in adirection orthogonal to a lengthwise direction of the signal line,passing through the first ground, the second ground, and the dielectricin a vertical direction, formed by filling a plurality of trenches,which are formed in the vertical direction such that the first groundand the second ground are electrically connected, with conductors,wherein one side of the conductor is surrounded by the trench to facethe signal line in a widthwise direction of the signal line and theother side of the conductor is exposed to the outside; and a cover layerdisposed below the first ground and having grooves formed therein suchthat the ground connection portions are exposed at certain intervals.

The flexible circuit board may further include printed circuit boardground pads coupled to the grooves via solder, wherein the printedcircuit board ground pads may be formed to be long in the widthwisedirection of the signal line at both sides of the signal line interposedtherebetween, an inner side of each of the printed circuit board groundpads in the widthwise direction may be formed in a shape the same as ashape of the groove, and an outer side of each of the printed circuitboard ground pads in the widthwise direction may be formed in a shapewhich extends to have a size equal to a diameter of the groove.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description that follows, embodiments are described asillustrations only since various changes and modifications will becomeapparent to those skilled in the art from the following detaileddescription. The use of the same reference numbers in different figuresindicates similar or identical items.

FIG. 1 is a view illustrating a flexible circuit board mounted on aprinted circuit board;

FIGS. 2 to 4 are views illustrating a first example embodiment of thepresent invention;

FIGS. 5 to 7 are views illustrating a second example embodiment of thepresent invention; and

FIGS. 8 to 11 are views illustrating a third example embodiment of thepresent invention.

DETAILED DESCRIPTION

As a first example embodiment for solving a problem in that surfacemounter technology (SMT) is not properly performed when a flexiblecircuit board 10 is not properly mounted on a printed circuit board 20,as shown in FIGS. 2 and 3, the present invention includes a first ground100, a second ground 200, a signal line 300, a dielectric 400, a coverlayer 500, and position alignment portions 550.

The signal line 300 is disposed between the first ground 100 and thesecond ground 200.

The dielectric 400 is disposed between the first ground 100 and thesignal line 300 and between the second ground 200 and the signal line300.

The cover layer 500 is disposed below the first ground 100.

Openings O are formed in the cover layer 500 at certain intervals suchthat the first ground 100 is exposed through the openings O.

The first ground 100 exposed at the cover layer 500 becomes a flexiblecircuit board ground pad 11. The flexible circuit board ground pad 11and a printed circuit board ground pad 21, which is formed on theprinted circuit board 20, are coupled by thermally melting solder 22therebetween.

An area of the printed circuit board ground pad 21 may be greater thanor equal to an area of the opening O.

The position alignment portion 550 is formed across the opening O tobisect the area of the opening O.

A bonding position of an upper side x and a lower side y of the openingO bisected by the position alignment portion 550 is aligned by surfacetension generated when the solder 22 is melted.

For example, when an area of the printed circuit board ground pad 21 incontact with the upper side x of the opening O is greater than an areathereof in contact with the lower side y of the opening O, a tensileforce is generated toward the lower side y of the opening O due to thesurface tension until the areas of the printed circuit board ground pad21 in contact with the upper side x and the lower side y are equal toeach other. As a result, the flexible circuit board 10 is moveddownward, thereby aligning the bonding position.

The position alignment portion 550 may be formed to have a diagonalshape rather than a horizontal shape so as to align the bonding positionnot only in a vertical direction but also in a horizontal direction.

Due to the diagonal shape of the position alignment portion 550, an areaof an upper left side x1 of the opening O bisected by the positionalignment portion 550 is equal to an area of a lower right side y2 ofthe opening O bisected by the position alignment portion 550. Inaddition, an area of an upper right side x2 of the opening O bisected bythe position alignment portion 550 is equal to an area of a lower leftside y1 of the opening O bisected by the position alignment portion 550.

For example, when an area of the printed circuit board ground pad 21 incontact with the left sides x1 and y1 of the opening O is greater thanan area thereof in contact with the right sides x2 and y2 of the openingO, a tensile force is generated toward the right sides x2 and y2 of theopening O due to the surface tension until the areas of the printedcircuit board ground pad 21 in contact with the left sides x1 and y1 andthe right sides x2 and y2 are equal to each other. As a result, theflexible circuit board 10 is moved rightward, thereby aligning thebonding position.

Since the bonding position is also aligned in the vertical direction asdescribed above, the bonding position is aligned in the vertical andhorizontal directions due to the diagonal shape of the positionalignment portion 550.

The diagonal shape of the position alignment portion 550 formed in theopening O may be symmetrical to a diagonal shape of a position alignmentportion 550 formed in an opening O adjacent to the opening O.

The symmetrical diagonal shapes may be consecutively repeated in anextending direction of the signal line 300. Alternatively, as shown inFIG. 4, the same diagonal shapes may be repeated, and then, symmetricaldiagonal shapes may be repeated.

In addition, the opening O may be formed to have a width equal to awidth of the flexible circuit board 10.

As described above, the bonding position may be aligned in the verticaland horizontal directions due to the diagonal shape of the positionalignment portion 550.

As a second example embodiment for solving a problem in that SMT is notproperly performed when a flexible circuit board 10 is not properlymounted on a printed circuit board 20, as shown in FIGS. 5 and 6, thepresent invention includes a first ground 100, a second ground 200, asignal line 300, a dielectric 400, via holes 600, and a cover layer 500.

Since the first ground 100, the second ground 200, the signal line 300,and the dielectric 400 are the same as those of the first exampleembodiment described above, descriptions thereof will be omitted.

The via holes 600 are formed in a direction orthogonal to a lengthwisedirection of the signal line 300 and pass through the first ground 100,the second ground 200, and the dielectric 400 in a vertical direction.The via holes 600 are formed by filling a plurality of holes, which areformed in the vertical direction such that the first ground 100 and thesecond ground 200 are electrically connected, with conductors.

The cover layer 500 is disposed below the first ground 100 and hasopenings O formed therein such that the via holes 600 are exposed atcertain intervals.

As shown in FIG. 7, printed circuit board ground pads 21 are formed tobe long in a widthwise direction of the signal line 300 at both sides ofthe signal line 300 interposed therebetween. An inner side of theprinted circuit board ground pad 21 in the widthwise direction is formedin a shape the same as a shape obtained by bisecting the opening O alonga center thereof, and an outer side thereof is formed in a shape whichextends to have a size equal to a diameter of the opening O.

Since the shape of the opening O and the shape of the printed circuitboard ground pad 21 partially have the same area in the widthwisedirection of the signal line 300, a tensile force is generated in thewidthwise direction of the signal line 300. Thus, a bonding position isaligned.

As described above, the bonding position is aligned due to the shape ofthe printed circuit board ground pad 21.

As a third example embodiment for solving a problem in that SMT is notproperly performed when a flexible circuit board 10 is not properlymounted on a printed circuit board 20, as shown in FIGS. 8 to 10, thepresent invention includes a first ground 100, a second ground 200, asignal line 300, a dielectric 400, ground connection portions 700, and acover layer 500.

Since the first ground 100, the second ground 200, the signal line 300,and the dielectric 400 are the same as those of the first exampleembodiment described above, descriptions thereof will be omitted.

The ground connection portions 700 are formed in a direction orthogonalto a lengthwise direction of the signal line 300 and pass through thefirst ground 100, the second ground 200, and the dielectric 400 in avertical direction. The ground connection portions 700 are formed byfilling a plurality of trenches, which are formed in the verticaldirection such that the first ground 100 and the second ground 200 areelectrically connected, with conductors. One side of the conductor issurrounded by the trench to face the signal line 300 in a widthwisedirection of the signal line 300, and the other side of the conductor isexposed to the outside.

The cover layer 500 is disposed below the first ground 100 and hasgrooves D formed therein such that the ground connection portions 700are exposed at certain intervals.

As shown in FIG. 11, printed circuit board ground pads 21 are formed tobe long in the widthwise direction of the signal line 300 at both sidesof the signal line 300 interposed therebetween. An inner side of theprinted circuit board ground pad 21 in the widthwise direction is formedin a shape the same as a shape of the groove D, and an outer sidethereof is formed in a shape which extends to have a size equal to adiameter of the groove D.

Since the shape of the groove D and the shape of the printed circuitboard ground pad 21 partially have the same area in the widthwisedirection of the signal line 300, a tensile force is generated in thewidthwise direction of the signal line 300. Thus, a bonding position isaligned.

As described above, the bonding position is aligned due to the shape ofthe printed circuit board ground pad 21.

A bonding position is aligned in vertical and horizontal directions dueto a diagonal shape of a position alignment portion 550.

A bonding position is aligned due to a shape of a printed circuit boardground pad 21.

DESCRIPTION OF REFERENCE NUMERALS  10: flexible circuit board  11:flexible circuit board ground pad  20: printed circuit board  21:printed circuit board ground pad  22: solder 100: first ground 200:second ground 300: signal line 400: dielectric 500: cover layer 550:position alignment portion 600: via hole 700: ground connection portionO: opening D: groove

We claim:
 1. A flexible circuit board with improved bonding positionaccuracy, comprising: a signal line disposed between a first ground anda second ground; a dielectric disposed between the first ground and thesignal line and between the second ground and the signal line; via holesformed in a direction orthogonal to a lengthwise direction of the signalline, configured to pass through the first ground, the second ground,and the dielectric in a vertical direction, and formed by filling aplurality of holes, which are formed in the vertical direction such thatthe first ground and the second ground are electrically connected, withconductors; a cover layer disposed below the first ground and havingopenings formed therein such that the via holes are exposed at certainintervals; and a printed circuit board including printed circuit boardground pads coupled to the openings via solder, wherein the printedcircuit board ground pads are formed to be long only in a widthwisedirection perpendicular to the lengthwise direction of the signal lineat both sides of the signal line interposed therebetween, an inner sidetowards the signal line of each of the printed circuit board ground padsin the widthwise direction is formed in a shape the same as a shapeobtained by bisecting the opening along a center thereof, and an outerside away from the signal line of each of the printed circuit boardground pads is formed in a shape which extends only in the widthwisedirection to have a size equal to a diameter of the opening.